Aswitched mode power supplyis an electronicpower supplythat incorporates a switching regulator toconvert electrical powerefficiently. Like other power supplies, an SMPS transfers power from a source, likemains powerto a load, such as apersonal computer, while convertingvoltageandcurrentcharacteristics. Unlike alinear power supply, the pass transistor of a switching-mode supply continually switches between low-dissipation, full-on and full-off states, and spends very little time in the high dissipation transitions, which minimizes wasted energy. Ideally, a switched-mode power supply dissipates no power.Voltage regulationis achieved by varying the ratio of on-to-off time. In contrast, a linear power supply regulates the output voltage by continually dissipating power in the passtransistor. This higher power conversion efficiency is an important advantage of a switched-mode power supply. Switched-mode power supplies may also be substantially smaller and lighter than a linear supply due to the smaller transformer size and weight.
Switching regulators are used as replacements for linear regulators when higher efficiency, smaller size or lighter weight are required.